Anti-Sm: its predictive value in systemic lupus erythematosus.

The clinical manifestations of 131 rheumatic disease patients with anti-Sm antibody were studied. A variety of standard tests was utilized in the study, namely, the FANA test with mouse kidney as substrate for the assay of ANA, the Crithidia test for anti-double stranded DNA (anti-dsDNA) and double immunodiffusion for detecting antibodies to extractable nuclear antigens. The patients were grouped according to the presence of anti-Sm alone, or anti-Sm with some other antibodies. There were 17 with anti-Sm alone; 55 with anti-Sm+anti-RNP; 15 with anti-Sm+anti-dsDNA; and 44 with anti-Sm+anti-RNP. The result of our study showed that although anti-Sm could be found in other diseases, it was exclusively detected in SLE only if anti-dsDNA was also present. Further, the SLE patients with anti-Sm alone had more frequent central nervous system manifestations than other groups of patients. The renal manifestation was observed more frequently in the group of SLE patients with anti-Sm+anti-dsDNA (92.9%). Among other major manifestations, haematologic involvement had a tendency to be less common in the group of patients with anti-Sm alone. The study concludes that the presence of anti-Sm antibody may be of some value to predict the clinical outcome.